High caloric diets enriched with saturated fatty acids (SFA) or carbohydrates (CARB) were evaluated in subjects with normal and impaired glucose tolerance (NGT or IGT). Both diets were compared to a standard eucaloric American Heart Association (AHA) control diet in a series of crossover studies. Whole body insulin resistance was estimated as steady state plasma glucose (SSPG) concentrations during the last 30 min of a 3-h insulin suppression test.
SSPG was increased after a 24-h SFA diet (by 83 ± 74% vs. control, n = 38) in the entire cohort, which was comprised of participants with NGT (92 ± 82%, n = 22) or IGT (65 ± 55%, n = 16) (all p < 0.001). SSPG was also increased after a single SFA breakfast (55 ± 32%, p = 0.008, n = 7). The increase in SSPG was less pronounced after an overnight fast following a daylong SFA diet (24 ± 31%, p = 0.04, n = 10), and further attenuated 24 h after returning to the control diet (19 ± 35%, p = 0.09, n = 11). SSPG was not increased after a 24-h CARB diet (26 ± 50%, p = 0.11, n = 12).
A short-term SFA-enriched diet induced whole body insulin resistance in both NGT and IGT subjects. Insulin resistance persisted overnight after the last SFA meal and was attenuated by one day of a healthy diet. This model offers opportunities for identifying early mechanisms and potential treatments of dietary saturated fat induced insulin resistance.